The present invention relates to a portable electronic apparatus such as a portable computer or a portable information tool and an extension apparatus for extending the function of the electronic apparatus. The invention also relates to an electronic apparatus system comprising the electronic apparatus and the extension apparatus, which are integrated in the form of one module.
To have an increased commercial value, it is greatly important for electronic apparatuses, such as portable computers, to excel in portability. The portable computers recently developed therefore have a housing that is thinner and lighter than before. They are small and light enough to be put into bags and the like and to be carried with.
A portable computer is compact, having a thin housing. Hence, it is difficult for the housing to have spaces for accommodating connectors for connecting input/output devices to the computer, a floppy disk drive, and a CD-ROM drive. For this reason, the portable computers recently developed each have a dedicated extension connector. The extension connector connects the computer to an extension apparatus called "docking station." The function of the portable computer is thereby so extended that the portable computer can perform functions that are comparable with those of desktop computers.
Conventional extension apparatuses have a box-shaped base each. The base has a flat mount section. The mount section is small enough to be placed on the housing of a portable computer. On the mount section, there are arranged relay connectors. The relay connectors will be electrically connected to the extension connectors of a portable computer when the housing of the computer is mounted on the mount section. The base contains various extension components such as a circuit board, a floppy disk drive, a CD-ROM drive and speakers. The circuit board has a number of circuit parts mounted on it. Various connectors and ports are arranged on the side or back of the base. These connectors and ports are provided to connect peripheral devices such as a keyboard, a display and a printer to the computer. The connectors and ports will be electrically connected to the portable computers by the relay connectors and extension connectors when the housing is mounted on the mount section of the base. The logic addresses and control signal paths (e.g., buses) of the portable computer are electrically connected to those of the extension apparatus. This extends the function of the portable computer.
The portable computers that have been recently developed have an MPU (microprocessor unit) each. The MPU is designed to process useful multimedia information that represents characters, sound, speeches and images. MPUs have been improved to process information at a higher speed and to perform more functions. The faster an MPU processes information and the more functions it performs, the more electric power it will consume. There is the trend that the heat, which the MPU generates while operating, increases in proportion to the power the MPU consumes. Once an MPU that generates much heat while operating is incorporated into the housing of a portable computer, it is necessary to enhance the efficiency of radiating the heat.
To this end, the housing of the conventional portable computer incorporates a heat sink thermally connected to the MPU and a fan unit for applying cooling air to the heat sink, thereby to cool the MPU. If the portable computer is connected to an extension apparatus to make the MPU perform complicated operations, the MPU will generate more heat. An extension apparatus designed to radiate the heat efficiently is known. The base of this extension apparatus contains a fan unit, and the mount section of the base has an exhaust port. The fan unit applies cooling air to the exhaust port. When the housing of the computer is mounted on the mount section of the base, the exhaust port comes to oppose the bottom wall of the housing. Thus, the cooling air sent through the exhaust port is applied onto the bottom wall of the housing. The housing is thereby cooled from outside. Further, the fan unit cools the MPU. The efficiency of radiating heat from the portable computer can therefore be enhanced.
The inner space of the housing, which may accommodate components, is much limited, however, because the portable computer is thin and compact. Hence, the heat sink and the fan unit need to be small enough to be incorporated into the housing. The efficiency of radiating heat from the MPU is proportional to the heat-radiating area of the heat sink and the rate of applying cooling air. If the heat sink and the fan unit are small, the heat-radiating area and the air-applying rate will proportionally decrease. The heat-radiating efficiency may not be high enough to radiate all heat that the MPU radiates while operating. In other words, the MPU may not be cooled sufficiently.
The amount of heat transmitted from the MPU to the housing is no more than a fraction of all heat that the MPU generates. Even if the housing is positively cooled with the cooling air applied onto the bottom wall of the housing, it contributes only a little to the radiation of heat from the MPU. The MPU cannot be cooled with efficiently.
Consequently, the temperature of the MPU may rise above the maximum operating temperature of the MPU. If the temperature of the MPU exceeds the maximum operating temperature, the information-processing speed of the MPU may decrease. In the worst case, the MPU may stop operating at all. In short, the MPU may fail to operate at its maximum capacity.